I was not talking about the tx that we used to use, not analog or audio channel, it must be a special made one, a true datalink. For example, a GSM cell phone could support a transfer rate of 223Kb/s, a Wifi data link 54Mb/s, something like that. And a 2nd tx to monitoring, this one some we used to use. It's not a simple project, I know.
Regarding to the compression, yes there are very powerful and small low power chipsets for video compression, the ones that are used in the new HDTV portable video cameras, ok it are not for sale to us mortals, but they exist.
Regards

Hi,
I'm new to the forum, but I will give my 2 pennies.
If the hi-res is not a goal, you can use a conventional camera with an anamorphic lens (maybe a C mount). Little space to explain here, but at coarse it "compresses optically" the image and at the playback in a 16:9 display it is decompressed. Widescreen DVDs works this way.
If you will not pilot the plane through the hi-res downlink, you can use a data channel for the mpeg2 compression and a analog low-res downlink for piloting the plane.
Regards